I realize there have been historic floods around the Frio through Tilden, but (once again because I've been paying attention) I've under no circumstances found the Frio set a drop into the NUECES watershed. Your neighborhood College or Cooperative Extension may give laboratory soil testing. Examine the web site or https://jeffreyorqpx.eedblog.com/37231040/bermuda-grass-sod-an-overview